In many cases, a power circuit of a control unit included in the laser machining apparatus is mounted to an electric storage component such as a capacitor, the configuration being such that power supply voltage of the control unit is maintained even when a power-down occurs for a short period of time. However, if an abnormality occurs in equipment such as an inverter and a power source for excitation, the equipment being operated by an external power source and included in the laser machining apparatus, a recovery to the same state as before the power-down requires a large amount of time. Hence, there is a decrease in the operating ratio of the laser machining apparatus in regions having a high frequency of the power-down.
There are a variety of methods for protecting the apparatus from the power-down of the external power source. For example, one known method is a method of causing an operation by an internal power source when a power outage occurs, measuring a period of power outage, after the power has been restored, continuing the operation when the power outage time is shorter than a predetermined period of time and stopping the operation when the power outage time is longer than the predetermined period of time (e.g., Japanese Unexamined Patent Publication No. 5-000199 (JP 5-000199 A)). This prior art includes: a storage means for storing a progress status of an operation process; a detection means for detecting whether electric power is supplied from an external power source; a time measurement means for measuring power outage time of the external power source; an internal power source for back up the storage means and the time measurement means when the power outage of the external power source occurs; and a control means for continuing the interrupted operation process when the power outage time is within the predetermined period of time and stop the operation process when exceeding the predetermined period of time upon an interruption of the operation process due to the power outage of the external power source and upon restarting supplying the power. This prior art is targeted on electric products for home use and is difficult to be applied in an as-is state to the laser machining apparatus mounted to a CNC, a gas laser oscillator, an inverter and a laser power source.
Further, a power restoration processing method of a power source for an information processing apparatus is known as the power restoration processing method of the power source (e.g., Japanese Examined Patent Publication No. 7-095253 (JP 7-095253 B)). This prior art includes a power source unit, a power source control unit and an information processing unit, in a power restoration processing method of a power source for an information processing apparatus with the power source control unit controlling a supply of the power source to the information processing unit from the power source unit, the configuration being such that the power source control unit includes: a timer means for starting of a power outage signal; a power outage processing unit for storing a power outage state in storage means through the power outage signal; and a power restoration processing unit for starting the power outage signal that is off when a time-out output of the timer means occurs, and the power restoration processing unit for generating a control signal for instructing the power source unit to switch on the power source when reading a power outage state of the storage means upon the start-up. This prior art is directed to an information processing apparatus and is difficult to be applied in the as-is state to the laser machining apparatus mounted to the CNC, the gas laser oscillator, the inverter and the laser power source. This prior art performs a power restoration process when the power outage time is shorter than the time-out time. However, the prior art does not mention a case of the power outage time being longer than the time-out time.
When powering down of the laser machining apparatus, an abnormality occurs in the inverter and the power source for the excitation of a laser gas blowing device mounted in the laser oscillator when the power-down time is short, and this abnormal state is maintained even after the power restoration and is not cancelled unless these equipment are stopped. Conventionally, when an abnormality occurs in the equipment of the laser machining apparatus due to the power-down, the recovery to the state before the occurrence of the power-down involves, at first, cancelling the abnormality of the equipment by stopping the laser machining apparatus and performing the same start-up as normal, resulting in a necessity for a labor and a large amount of time.
The laser machining apparatus being invariably stopped irrespective of the power-down time also requires its start-up operation in the same way as described above for the recovery to the state before the power-down, resulting in the necessity of labor and a large amount of time.
It is an object of the present invention to provide a laser machining apparatus recovering to a state before power-down in a short period of time after power restoration of an external power source temporarily decreasing in its electric power.